The old brass helicoid grease is not the same as the new stuff

Went to regrease a 50mm lens from 1972 last week and noticed the original grease was still smooth as silk. The replacement grease I put in six months ago on another lens is already stiffening up. Seems like the modern lithium greases just don't hold up the same way the old molybdenum blends did. I know some of the synthetics are supposed to be better, but I've seen three repairs come back with focus drag that were fine for a decade before. Anyone else finding this with newer grease or is it just the brands I'm using? I'm in Pittsburgh and order from two different suppliers, so I don't think it's a storage issue.

2 comments

2 Comments

troychen2d ago

Wait, the old grease is still smooth after fifty years but the new stuff goes stiff in six months? That's wild. I've got a 1968 Takumar that's still buttery, and I've had to redo a 90s lens twice in the last three years with different brands. The old moly stuff really does seem to have some magic in it, maybe it's the way it clings to the threads or just doesn't dry out the same. You're not dealing with cheap stuff either, two suppliers in Pittsburgh means you're probably checking what you buy. Makes me wonder if we're all just chasing specs while the old recipes had something the labs can't copy.

alice_allen52d ago

Ask @troychen if he's ever tried mixing a bit of the old moly into the new stuff, or if the suppliers just shrug when you bring up the shelf life? Curious if anyone's actually tested the old grease under a microscope to see what makes it cling like that.